As described in my copending U.S. Pat. applications Ser. Nos. 873,340 (filed Jan. 30, 1978) and 729,515 (filed Oct. 4, 1976) now Pat. No. 4,165,295, organic stripping solutions including sulfonic acids are known in stripping agents for removing polymeric organic substances such as photoresists from metallized inorganic substrates. While such stripping agents are effective in removing the polymeric substances, they also have a tendency, especially in the presence of water, to corrode the metal, particularly aluminum and titanium. In my above two applications, I describe inhibitors for such stripping agents which reduce the metal corrosion rate. Such systems include fluoride, especially as hydrogen fluoride. It has now been found that nitrile compounds reduce the loss of fluoride through vaporization of HF, and also enhance the corrosion inhibition properties of the fluoride.